Device at mixing devices for mixing pulverulent and liquid substances with each other for the manufacture of medical products

ABSTRACT

The present invention relates to a device at mixing devices for mixing pulverulent and liquid substances with each other for the manufacture of medical products, wherein a displaceable piston means ( 17 ) has at least one groove ( 22 ) extending around said piston means ( 17 ) and at least one sealing ring ( 23 ) is located in said groove ( 22 ). At least one connecting passage ( 22   e ) is provided for preventing a liquid substance ( 21 ) from generating or building up such a pressure in an inner space ( 22   d ) in the groove ( 22 ) within or behind the sealing ring ( 23 ) that said pressure presses the sealing ring ( 23 ) in a direction outwards (F) relative to the groove ( 22 ) towards a surrounding wall ( 1   a ) of the mixing device ( 1 ) and prevents or counteracts flow of the liquid substance ( 21 ) past the piston means ( 17 ) when said piston means ( 17 ) is displaced.

[0001] The present invention relates to a device at mixing devices formixing pulverulent and liquid substances with each other for themanufacture of medical products. The pulverulent substance is providedin a first space on one side of a displaceably mounted piston means andthe liquid substance in a second space on the opposite side of saidpiston means. The piston means is displaceable by a displacement means.The piston means has at least one groove extending around said pistonmeans, at least one sealing ring being located in said groove. Thesealing ring is provided to cooperate, in a sealing position, with thepiston means and with a wall of the mixing device surrounding saidpiston means, whereby the piston means and sealing ring sealinglyseparate the first and second spaces from each other for preventing thepulverulent substance and the liquid substance from mixing with eachother when mixing should not occur. The sealing ring is provided, whenloaded by the liquid substance during displacement of the piston meansin a direction towards the second space containing the liquid, to bepressed inwards in the groove by the liquid substance and thereby atleast partially being brought to leave its sealing position such thatthe liquid substance may flow into the first space containing thepulverulent substance for mixing therewith.

[0002] Mixing devices for mixing a pulverulent polymer and a liquidmonomer for the manufacture of bone cement are previously known fromU.S. Pat. Nos. 5,328,262 and 5,551,778. In the embodiment of U.S. Pat.No. 5,551,778, the liquid substance—here a monomer—is located in aclosed container. This container is placed in a mixing chamber in whicha pulverulent substance—here a polymer—is also located. The containerwith the liquid substance is opened by penetrating the wall thereof,whereby the liquid and pulverulent substances come in contact with eachother and may be mixed with each other.

[0003] The object of the present invention has been to present a devicein which the liquid and pulverulent substances can be placed in twospaces which are separated from each other by a piston means having asealing ring, and this is arrived at according to the invention by meansof the characterizing features of primarily subsequent claim 1.

[0004] Since the invention has said characterizing features, it isachieved that the liquid and pulverulent substances can be located onopposite sides of a piston means having a sealing ring which has aneffective sealing capacity when required and an effective transmittingor permeable capacity when this is required.

[0005] The invention will be further described below with reference tothe accompanying drawings, in which

[0006]FIG. 1 is a longitudinal section through a mixing device having adevice according to the invention;

[0007]FIG. 2 schematically shows the mixing device of FIG. 1 duringdisplacement of a piston means forming part thereof;

[0008]FIG. 3 is a generous magnification of parts of the piston meansand surrounding members of the mixing device of FIG. 2; and

[0009]FIG. 4 illustrates the mixing device of FIG. 1 when bone cement isfed out of said mixing device.

[0010] The mixing device 1 illustrated in the drawings includes acylindrical member 2 which eventually consists of two parts 2 a, 2 bwhich are screwed together. One end opening of the cylindrical member 2is closed by means of a cap 3 or similar screwed thereon, while theopposite second end opening is closed by means of a closing piston 4 orsimilar. The cap 3 has a through hole 5 through which a displacementmeans 6 extends into the cylindrical member 2. The displacement means 6may include a rod or similar and is sealingly mounted at the cap 3, andit is displaceable in its longitudinal direction and rotatable relativeto its longitudinal axis. Inside the cylindrical member 2, thedisplacement means 6 has at least a mixing member 7 with throughopenings 8 or similar. By displacing and/or rotating the displacementmeans 6, it can be used as mixing means for mixing bone cement in thecylindrical member 2 by using the mixing member 7 therefor. Thedisplacement means 6 may, outside the cylindrical member 2, have ahandle member 9 which is engaged for displacement and/or rotation ofsaid displacement means 6.

[0011] The cap 3 preferably also includes a connecting member 10 forconnection of a hose 11 or similar in order to join the cylindricalmember 2 to a vacuum generating device 12, e.g. a pump, which is adaptedto generate a vacuum in the cylindrical member 2. There may be a filter13 in the cylindrical member 2 and this filter 13 is adapted to preventconstituents of bone cement from being sucked into the hose 11.

[0012] When bone cement shall be discharged from the cylindrical member2, the hose 11 is released from the connecting member 10 and instead, adischarge member 14, which preferably is tubular, is connected to theconnecting member 10 so that bone cement can be discharged through theconnecting member 10 and the discharge member 14.

[0013] The closing piston 4 may have exterior coupling members 15 orsimilar, which can cooperate with interior coupling members 16 orsimilar on the cylindrical member 2 such that the closing piston 4 canbe connected to said cylindrical member 2 at said second end openingsuch that it adheres thereto. The coupling members 15, 16 permitdisengagement of the closing piston 4 from the cylindrical member 2 e.g.by rotating said closing piston 4 relative to said cylindrical member 2.After this disengagement, the closing piston 4 may be moved into thecylindrical member 2.

[0014] In the cylindrical member 2 there is provided a piston means 17which divides said cylindrical member 2 into a first space 18 for apulverulent substance 19, here a polymer, and a second space 20 for aliquid substance 21, here a monomer. The piston means 17 has a groove 22which extends therearound and which is open in a direction towards asurrounding wall 1 a of the mixing device 1. The groove 22 has, in theillustrated embodiment, two parallel or substantially parallel sidewalls 22 a, 22 b which are directed inwards towards the central parts ofthe piston means 17. The groove 22 also has a bottom 22 c which in theillustrated embodiment extends in an axial direction relative to thepiston means 17 or which extends essentially in this direction. In thisgroove 22, there is located a sealing ring 23 which preferably has acircular or substantially circular cross-sectional shape and whichpreferably is elastic. In a normal shape, the sealing ring 23 is in asealing position A (see FIG. 1) in which it sealingly engages the sidewalls 22 a, 22 b of the groove 22 and the wall 1 a, which means that thepiston means 17 along with the sealing ring 23 sealingly separates thefirst and second spaces 18, 20 from each other for preventing thepolymer 19 and monomer 21 from mixing with each other when mixing shouldnot occur.

[0015] For mixing the polymer 19 and monomer 21 with each other, thepiston means 17 is pressed by the displacement means 6 in an axialdirection B relative to the mixing device 1 towards the second space 20.The sealing ring 23 is thereby loaded by the monomer 21 such that saidmonomer 21 presses the sealing ring 23 in a direction C into the groove(see FIG. 3) to an opening position D in which it at least partially hasdisengaged the wall 1 a and opened at least a through-flow passage 24through which the monomer 21 can flow from the second space 20 into thefirst space 18 (arrow E) to the polymer 19 located therein for mixingtherewith.

[0016] During said displacement of the piston means 17 in direction Btowards the second space 20, it has been found that monomer 21 might bepressed into an inner space 22 d in the groove 22 within or behind thesealing ring 23, and in this inner space 22 d it can generate or buildup a pressure which affects the sealing ring 23 to be unintentionallypressed in a direction F outwards relative to the groove 22 towards thewall 1 a, such that it at least temporarily prevents monomer 21 fromflowing from the second space 20 to the first space 18.

[0017] In order to prevent that the sealing ring 23 is pressed inoutwards direction F, i.e. blocking the monomer flow E through thethrough-flow passage 24, there is in one side wall 22 a of the groove 22provided one or preferably several connecting passages 22 e whichconnect the inner space 22 d in the groove 22 with the through-flowpassage 24 so that the monomer 21 can not generate said pressure in theinner space 22 d but instead, the pressure therein will be substantiallyequal to the pressure in the through-flow passage 24 when the pistonmeans 17 is displaced.

[0018] The connecting passage or passages 22 e may be located in theside wall 22 a such that they extend from the axially directed outerside of the piston means 17 to the bottom 22 c of the groove 22, i.e.such that they connect the through-flow passage 24 and the inner space22 d to each other.

[0019] Furthermore, the connecting passage or passages 22 e may belocated either in the side wall 22 a lying closest to the first space18, but it or they may alternatively be located in the opposite sidewall 22 b or in both side walls 22 a and 22 b. There may be a pluralityof connecting passages 22 e which are provided distributed around thegroove 22.

[0020] Said means for preventing pressure build-up in the inner space 22d of the groove 22 may of course also be of another type than one ormore connecting passages 22 e in the side walls 22 a and/or 22 b of thegroove 22. Connecting passages may e.g. be provided in other ways in thepiston means 17 and as an alternative to or in combination withconnecting passages in the piston means 17 there may be connectingpassages in the sealing ring 23.

[0021] Before mixing the polymer 19 and monomer 21, the piston means 17and sealing ring 23 thus define a tight or impermeable partition wallbetween the first and second spaces 18, 20 and the sealing ring 23contributes thereto since it in its sealing position A simultaneouslyengages the side walls 22 a, 22 b of the groove 22 and the wall 1 a.Thus, when the piston means 17 is displaced by the displacement means 6in direction B towards the second space 20, the sealing ring 23 will bepressed inwards in direction C to its opening position D and therebyrelease or pass through monomer 21 from the second space 20 to thepolymer 19 in the first space 18.

[0022] The displacement of the piston means 17 continues until thepiston means 17 engages the closing piston 4, whereby all monomer 21will be located in the same space as the polymer 19. The piston means 17may have such connecting portions 17 a and the closing piston 4 suchcorresponding connecting portions 4 a that the piston means 17 by meansof the displacement means 6 can be pressed onto and fixed on the closingpiston 4, whereby it is achieved that the piston means 17 can bedisplaced in the mixing device 1 together with the closing piston 4 as aunit.

[0023] When the polymer 19 and monomer 21 are situated in one and samespace (consisting of the previous spaces 18 and 20), mixing thereofoccurs by means of the displacement means 6, which is displaced in axialdirection B and rotated about its longitudinal axis such that its mixingmember 7 mix the polymer 19 and monomer 21 with each other. This mixingoccurs preferably while generating a vacuum in the mixing device 1 bymeans of the vacuum generating device 12.

[0024] When mixing under vacuum is completed, the generation of vacuummay continue and the closing piston 4 may be released or disengaged fromthe mixing device 1, whereby said closing piston 4 and the piston means17 fixed thereon will be sucked into the mixing device 1 by beingaffected by said vacuum. Thereby, ready mixed bone cement 25 will becollected in the collecting member 26 closest to the connecting member10. When this is done, the hose 11 to the vacuum generating device 12may be disconnected from the connecting member 10 and instead, thedischarge member 14 can be connected thereto. Finally, a schematicallyillustrated discharge device 27 may be used for pressing the closingpiston 4 along with the piston means 17 in a discharge direction (seeFIG. 4) for discharging ready mixed bone cement 25 from the mixingdevice 1 through the discharge member 14.

[0025] The invention is not limited to the embodiment described above,but may vary within the scope of the subsequent claims. Thus, the devicemay be used at mixing devices for manufacturing completely differentmedical products than bone cement, whereby naturally the pulverulentsubstance 19 is another substance than a polymer and the liquidsubstance 21 another substance than a monomer. The mixing device 1 maybe of another construction than shown and this also goes for theconstruction of the members forming part thereof.

1. Device at mixing devices for mixing pulverulent and liquid substanceswith each other for the manufacture of medical products, wherein thepulverulent substance (19) is provided in a first space (18) on one sideof a displaceably mounted piston means (17) and the liquid substance(21) in a second space (20) on the opposite side of said piston means(17), wherein the piston means (17) is displaceable by a displacementmeans (6), wherein the piston means (17) has at least one groove (22)extending around said piston means (17), at least one sealing ring (23)being located in said groove (22), wherein the sealing ring (23) isprovided to cooperate, in a sealing position (A), with the piston means(17) and with a wall (1 a) of the mixing device (1) surrounding saidpiston means (17), whereby the piston means (17) and sealing ring (23)sealingly separate the first and second spaces (18, 20) from each otherfor preventing the pulverulent substance (19) and the liquid substance(21) from mixing with each other when mixing should not occur, andwherein the sealing ring (23) is provided, when loaded by the liquidsubstance (21) during displacement of the piston means (17) in adirection (B) towards the second space (20) containing the liquid, to bepressed inwards in a direction (C) in the groove by the liquid substance(21) and thereby at least partially being brought to leave its sealingposition (A) such that the liquid substance (21) may flow into the firstspace (18) containing the pulverulent substance (19) for mixingtherewith, characterized in that at least one connecting passage (22 e)is provided to permit flow of the liquid substance (21) out of an innerspace (22 d) in the groove (22) within or behind the sealing ring (23),for preventing the liquid substance (21) from generating or building upsuch a pressure in the inner space (22 d) that said pressure presses thesealing ring (23) in a direction outwards (F) relative to the groove(22) towards the surrounding wall (1 a) and prevents or counteracts flowof the liquid substance (21) in a direction (E) from the second space(20) to the first space (18) when the piston means (17) is displaced bythe displacement means (6) in direction (B) towards the second space(20).
 2. Device according to claim 1, characterized in that theconnecting passage (22 e) connects said inner space (22 d) to athrough-flow passage (24) through which the liquid substance (21) canflow from the second space (20) to the first space (18) such that thepressure in said inner space (22 d) substantially corresponds with or isequal to the pressure in the through-flow passage (24) when the pistonmeans (17) is displaced.
 3. Device according to claim 2, characterizedin that the connecting passage (22 e) is provided in at least one suchinwardly directed side wall (22 a) of the groove (22) which extendsbetween said through-flow passage (24) and said inner space (22 d). 4.Device according to claim 3, characterized in that the inwardly directedside wall (22 a) of the groove (22), provided with said connectingpassage (22 e), is one of two inwardly directed side walls (22 a, 22 b)of said groove (22) and situated closest to the first space (18) withthe pulverulent substance (19).
 5. Device according to any of claims2-4, characterized in that a plurality of connecting passages (22 e) areprovided distributed around the groove (22).
 6. Device according to anypreceding claim, characterized in that the sealing ring (23) is designedto engage, in a sealing position (A), at least one side wall (22 a) ofthe groove (22) provided with the connecting passage (22 e) or passages(22 e), as well as the surrounding wall (1 a) of the mixing device (1).7. Device according to any preceding claim, characterized in that thesealing ring (23) consists of such elastic material that it can becompressed from a sealing position (A) to an opening position (D). 8.Device according to any preceding claim, characterized in that the firstand second spaces (18, 20) form part of a mixing device (1) formanufacturing bone cement (25) and that the pulverulent substance in thefirst space (18) is a polymer (19) and the liquid substance in thesecond space (20) a monomer (21) for the manufacture of said bone cement(25).
 9. Device according to claim 8, characterized in that said mixingdevice (1) includes a movable mixing means which is adapted for mixingpolymer (19) and monomer (21) and which is made up of said displacementmeans (6).
 10. Device according to claim 8 or 9, characterized in thatthe mixing device (1) includes a connecting member (10) for connectionof said mixing device (1) to a vacuum generating device (12) such that avacuum can be generated in the mixing device (1) during mixing ofpolymer (19) and monomer (21) and/or for collection of the bone cement(25) manufactured thereof in the mixing device (1).
 11. Device accordingto any of claims 8-10, characterized in that the mixing device (1) maybe connected to a vacuum generating device (12) which can generate sucha vacuum in said mixing device (1) that said vacuum affects the pistonmeans (17) to move in the mixing device (1) for collection of bonecement (25) in a collecting member (26) of the mixing device (1) fromwhich the bone cement (25) shall be discharged.
 12. Device according toany of claims 8-11, characterized in that the mixing device (1) includesa closing piston (4) for closing an end opening into a second space (20)for the monomer (21), that the closing piston (4) can be attached orfixed to the mixing device (1) in order to be held thereby during mixingof polymer (19) and monomer (21) and that the closing piston (4) isreleasable or disengageable from the mixing device (1) for being able tomove and/or be moved or displaced therein.
 13. Device according to claim11 or 12, characterized in that the piston means (17) and the closingpiston (4) can be connected to each other so that the closing piston (4)follows the piston means (17) if said piston means (17) is moved ordisplaced by a vacuum during collection of bone cement (25).
 14. Deviceaccording to claim 12 or 13, characterized in that the piston means (17)and the closing piston (4) are displaceable in the mixing device (1) bymeans of a discharge device (27) for discharging bone cement (25) fromthe mixing device (1).